The optical characteristics of certain optical components are temperature dependent. A typical example of such a component is a planar WDM component based on a phase array design (a design based on optical interferences between a large number of waveguides with different optical paths). Such components are usually packaged with a temperature regulation system utilizing a Peltier element. Reference may be made to H. Uetsuka et al. "Novel 1.times.N Guided-Wave Multi/demultiplexer for FDM", OFC'95 Technical Digest, pages 76, 77. However, this type of temperature compensation system has several disadvantages. It is expensive, it consumes relatively large amounts of power, and it requires a thermal exchange with the outside world. Moreover, it requires a dedicated power supply with AC input power at 110 V or 220 V.